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Home

Technical Articles

Database

Mysql Tutorial

Handling large object (BLOB/TEXT) data efficiently in MySQL

When dealing with large object data in MySQL, you need to pay attention to performance optimization issues. 1. Reasonably select the field type and select TEXT or BLOB subtypes of different capacity according to actual needs to avoid space waste and performance burden; 2. Avoid returning large fields in frequent queries, clearly list the required fields, use overlay indexes, or disassemble large fields to improve efficiency; 3. Optimize storage and IO strategies, such as external storage files, compressed content, partition management and reduce updates to large fields in transactions; 4. Use indexes carefully, TEXT/BLOB needs to specify the prefix length to build an index, reasonably set the prefix length and design the index effectiveness in combination with the query pattern.

Jul 07, 2025 am 02:13 AM

mysql

Securing Your MySQL Server Against Common Vulnerabilities

The following measures are required to strengthen the MySQL server: 1. Use strong passwords and restrict permissions, delete unnecessary users, avoid root remote login, and use GRANT and REVOKE to finely control access; 2. Close unnecessary services and ports, limit the access range of port 3306, and disable non-essential functions such as skip-networking and local_infile; 3. Regularly update the database version and enable log audit, and enable slow query, error, general and binary logs to track suspicious behavior; ensure database security by continuously paying attention to configuration, permissions, updates and monitoring.

Jul 07, 2025 am 02:06 AM

MySQL Security Server vulnerability

Benefits and Configuration of MySQL Connection Pooling

Using connection pools can improve database access efficiency and resource utilization. 1. Connection pool reduces connection establishment overhead, controls the number of connections, improves response speed, and optimizes resource usage, especially in high-concurrency scenarios such as e-commerce orders. 2. Common connection pooling components include HikariCP, Druid, C3P0 and DBCP in Java, as well as SQLAlchemy and mysql-connector-python in Python. 3. When configuring, you need to pay attention to parameters such as minimumIdle, maximumPoolSize, connectionTimeout, etc. For example, the recommended configuration of HikariCP is as minimum idle 5 and maximum connection 20. 4. Note

Jul 07, 2025 am 02:02 AM

Configuration mysql connection pool

Understanding MySQL transaction isolation levels

There are four types of transaction isolation levels in MySQL: ReadUncommitted, ReadCommitted, RepeatableRead, and Serializable. It is arranged in increments according to the degree of isolation, and RepeatableRead is used by default. 1. ReadUncommitted may cause dirty reading, non-repeatable reading, or phantom reading; 2. ReadCommitted prevents dirty reading, but may cause non-repeatable reading and phantom reading; 3. RepeatableRead prevents dirty reading and non-repeatable reading, and phantom reading is also avoided through the Next-Key lock mechanism in InnoDB; 4. Serializable prevents all concurrency problems, but

Jul 07, 2025 am 01:56 AM

mysql transaction isolation

Connecting to MySQL Database Using the Command Line Client

The most direct way to connect to MySQL database is to use the command line client. First enter the mysql-u username -p and enter the password correctly to enter the interactive interface; if you connect to the remote database, you need to add the -h parameter to specify the host address. Secondly, you can directly switch to a specific database or execute SQL files when logging in, such as mysql-u username-p database name or mysql-u username-p database name

Jul 07, 2025 am 01:50 AM

mysql Command line client

Managing Character Sets and Collations in MySQL

The setting of character sets and collation rules in MySQL is crucial, affecting data storage, query efficiency and consistency. First, the character set determines the storable character range, such as utf8mb4 supports Chinese and emojis; the sorting rules control the character comparison method, such as utf8mb4_unicode_ci is case-sensitive, and utf8mb4_bin is binary comparison. Secondly, the character set can be set at multiple levels of server, database, table, and column. It is recommended to use utf8mb4 and utf8mb4_unicode_ci in a unified manner to avoid conflicts. Furthermore, the garbled code problem is often caused by inconsistent character sets of connections, storage or program terminals, and needs to be checked layer by layer and set uniformly. In addition, character sets should be specified when exporting and importing to prevent conversion errors

Jul 07, 2025 am 01:41 AM

mysql character set

Practical Applications and Caveats of MySQL Triggers

MySQL triggers can be used to automatically execute SQL statements to maintain data integrity, automate tasks, and implement business rules, but they need to be aware of their limitations. 1. Can be used for audit logs, data verification, derived field updates and cascading operations; 2. Not suitable for high-performance requirements, complex logic, hidden side effects scenarios; 3. Best practices include keeping concise, good documentation, avoiding circular dependencies, paying attention to trigger timing, adequate testing, and paying attention to the limitation of allowing only one trigger per table and event. Rational use can improve efficiency, but excessive dependence can lead to maintenance difficulties.

Jul 07, 2025 am 01:37 AM

Database programming mysql trigger

Leveraging Geographic Information System (GIS) Features in MySQL

MySQLcanhandlebasicGIStaskswithitsspatialdatatypesandfunctions.ToworkwithgeographicdatainMySQL,usePOINTtostorecoordinates.UseST\_Distance\_Sphere()tofindpointswithinaradius.CreateSPATIALindexesforfastergeometrycontainmentchecks.UseMBRContains()orST\_

Jul 07, 2025 am 01:28 AM

mysql gis

Ordering Query Results with the ORDER BY Clause in MySQL

In MySQL queries, the ORDERBY clause can be used to display the results in a specific order. 1. Single-column sorting is implemented by specifying fields, default ascending order (ASC), or DESC can also be added to achieve descending order, such as SELECTname, priceFROMproductsORDERBYpriceDESC. 2. Multi-column sorting can define hierarchical sorting logic through multiple fields, such as SELECTname, age, created_atFROMusersORDERBYageASC, created_atDESC means that first ascending order by age and then descending order by registration time. 3. Usage techniques include using expression sorting, position numbering instead of column names (not recommended), and attention

Jul 07, 2025 am 01:28 AM

Restoring a MySQL Database from a Backup File

The key to restoring a MySQL database backup is to use the right tools and steps. 1. Preparation: Ensure that there is a complete .sql backup file, MySQL service is running, the name, username and password of the target database, or the ability to create a new library; 2. Recover using the command line: Use mysql-u username-p database name

Jul 07, 2025 am 01:18 AM

mysql backup

Effective Use of Temporary Tables in MySQL

A temporary table is a session-level object in MySQL, visible only to the current connection, and is suitable for processing intermediate result sets. The creation syntax is CREATETEMPORARYTABLE, which supports index and primary keys, and will be automatically deleted after the connection is disconnected. Applicable scenarios include: 1. When the intermediate results are reused multiple times; 2. The data volume is moderate but the logic is complex, and it needs to be processed in steps; 3. Avoid frequent access to the original table to reduce the burden on the database. Pay attention to when using: 1. Naming avoids conflicts with existing tables; 2. The same name cannot be created repeatedly for the same connection, and IFNOTEXISTS can be used to avoid errors; 3. Avoid frequent creation and deletion of temporary tables in transactions; 4. Appropriately add indexes according to query requirements to improve performance. Rational use can improve SQL efficiency and readability.

Jul 07, 2025 am 01:15 AM

mysql Temporary tables

Analyzing Query Execution Plans Using EXPLAIN in MySQL

To understand why MySQL query is slow, you must first use the EXPLAIN statement to analyze the query execution plan. 1. EXPLAIN displays the execution steps of the query, including the accessed table, join type, index usage, etc.; 2. Key columns such as type (connection type), possible_keys and key (index selection), rows (scanned rows), and Extra (extra information) help identify performance bottlenecks; 3. When using EXPLAIN, you should prioritize checking queries in the slow query log to observe whether there are full table scans (type:ALL) or high rows values; 4. Pay attention to the prompts such as "Usingfilesort" or "Usingtemporary" in the Extra column.

Jul 07, 2025 am 01:15 AM

mysql explain

Working with Date and Time Functions in MySQL Queries

The date and time functions in MySQL queries can be efficiently processed through 4 common methods. 1. Get the current time: NOW() returns the full time, CURDATE() returns only the date, CURTIME() returns only the time, it is recommended to select and pay attention to time zone issues as needed; 2. Extract some information: Use functions such as DATE(), MONTH(), YEAR(), HOUR() for WHERE and GROUPBY operations, but may affect the index performance; 3. Calculate the time difference: DATEDIFF() calculates the difference in the number of days of date, TIMEDIFF() calculates the short time difference, TIMESTAMPDIFF() supports flexible units, and is recommended for complex calculations; 4. Format output: DAT

Jul 07, 2025 am 01:10 AM

mysql date time

Exploring Various MySQL JOIN Operation Types

Commonly used JOIN types in MySQL include INNERJOIN, LEFTJOIN, RIGHTJOIN, FULLOUTERJOIN (requires simulation) and CROSSJOIN. INNERJOIN only returns the matching rows in the two tables; LEFTJOIN returns all rows in the left table, and the right table field is NULL when there is no match; RIGHTJOIN returns all rows in the right table, and the left table field is NULL when there is no match; FULLOUTERJOIN needs to be implemented through LEFTJOIN, RIGHTJOIN plus UNION to return all rows in the two tables; CROSSJOIN generates all combinations of rows in the two tables. Selecting the appropriate JOIN type can accurately obtain the required data.

Jul 07, 2025 am 01:08 AM

Database operations